In diseases such as infectious diseases, inflammatory lesions, degenerative lesions, calculus diseases, tumors and the like in nephric and urinary systems, a variety of particles appear in the urine depending on the individual diseases. The particles may include erythrocytes, casts, leukocytes, epithelial cells, yeast like fungi, spermatozoa and the like. Analysis of these particles in the urine is important for estimating the disease and the abnormal site in nephric and urinary systems. For example, erythrocytes are useful urinary particles for determining the presence or absence of bleeding in the route from the glomerulus of the kidney to the urethra.
A cast is a solid particle having a coagulation precipitate composed of Tamm-Horsfall mucoprotein and urinary plasma protein (principally albumin) as a basic component. The cast is formed principally in the distal renal tubule and the collecting tubule. While the cast composed exclusively of the basic component is called a hyaline cast, various components such as cells may be enclosed in the hyaline cast depending on the condition of the kidney or the renal tubule, with the result that a further degenerated cast could be formed. Therefore, the casts are useful urinary particles for grasping the disease condition and the degree of the disorder of the kidney and the renal tubule.
In analysis of the urinary particles such as casts and erythrocytes, a visual inspection is widely conducted by observing the precipitate (particles) obtained by centrifugal separation of the urine under a microscope. In recent years, an automated analysis method using a flow cytometer has been developed. For example, Patent Documents 1 to 4 disclose a method for analyzing urinary particles with a flow cytometer by measuring a urine sample treated with a diluting reagent, and a staining reagent containing a cyanine-based dye, 3,3′-dihexyl-2,2′-oxacarbocyanine iodide (DiOC6(3)) for staining urinary particles.
Meanwhile, the urine also contains the particles which extremely resemble the casts in shape, such as mucus threads and aggregates of bacteria or salts. Since the number of casts in a urine sample is the clinically important information, it is important for the detection of the casts to discriminate the casts from the particles which resemble the casts, such as mucus threads.